planetary science

All eyes are on Mars — and all ears, too. When NASA’s Perseverance rover touches down on the Red Planet on February 18, the landing will be recorded with sight, sound and maybe even touch.
The rover will cap off a month of Mars arrivals from space agencies around the world (SN: 7/30/20). Perseverance joins Hope, the first interplanetary mission from the United Arab Emirates, which successfully entered Mars orbit on February 9; and Tianwen-1, China’s first Mars mission, which arrived on February 10 and will deploy a rover to the Martian surface in May.
NASA will broadcast Perseverance’s landing on YouTube starting at 2:15 p.m. EST. The actual moment of touchdown is expected at approximately 3:55 p.m. EST. Perseverance is designed to explore an ancient river delta called Jezero crater, searching for signs of ancient life and collecting rocks for a future mission to return to Earth (SN: 7/28/20).
The rover will use the landing system pioneered by its predecessor, Curiosity, which has been exploring Mars since 2012 (SN: 8/6/12). But in a first for Mars touchdowns, this rover will record its own landing with dedicated cameras and a microphone.
As the craft carrying Perseverance zooms through the thin Martian atmosphere, three cameras will look up at the parachute slowing it down from supersonic speeds. When a rocket-powered “sky crane” platform lowers the rover to the ground, a fourth camera on the platform will record the rover’s descent. Another camera on the rover will look back up at the platform, and a sixth camera will look at the ground.
Perseverance will use the “sky crane” landing system pioneered by its predecessor, Curiosity. The landing involves dangling the rover from a floating platform on cables and touching down directly on its wheels.JPL-Caltech/NASA
Perseverance will use the “sky crane” landing system pioneered by its predecessor, Curiosity. The landing involves dangling the rover from a floating platform on cables and touching down directly on its wheels.JPL-Caltech/NASA
“The goal is to see the video and the action of getting from high up in the atmosphere down to the surface,” says engineer David Gruel of NASA’s Jet Propulsion Laboratory in Pasadena, who was the engineering lead for that six-camera system, called EDL-Cam. He hopes every engineer on the team has an image of the rover hanging below the descent stage as their computer desktop background six months from now.
Because it will take more than 11 minutes for signals to travel between Earth and Mars, the cameras won’t stream the landing movie in real time. And after Perseverance lands, engineers will be focused on making sure the rover is healthy and able to collect science data, so the landing videos won’t be among the first data sent back. Gruel expects to be able to share what the rover saw four days after landing, on February 22.

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Perseverance will also carry microphones to record first-ever audio of a Mars landing. Unlike the landing cameras, the microphones will continue to work after touchdown, hopefully helping the engineering team keep track of the rover’s health. Motors sound different when they get clogged with dust, for instance, Gruel says. The team will hear the sound of the rover’s wheels crunching across the Martian surface, and maybe the sound of the wind blowing.
“Are we going to hear a dust devil? What might a dust devil sound like? Could we hear rocks rolling down a hill?” Gruel asks. “You never know what we might stumble onto.”
Sound will add a way to share Mars with people who have trouble seeing, Gruel notes. “It might appeal to a whole other element of the population who might not have been able to experience past missions the same way,” he says.
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Watch NASA’s live coverage of the Perseverance landing here starting at 2:15 p.m. EST.
Elsewhere on Mars, the InSight lander will be listening to the landing too (SN: 2/24/20). The lander’s seismometer may be able to feel vibrations when two tungsten weights that Perseverance carried to Mars for stability smack into the ground before the rover lands, geophysicist Benjamin Fernando of the University of Oxford and colleagues report in a paper posted December 3 to eartharxiv.org and submitted to JGR Planets.
“No one’s ever tried to do this before,” Fernando says.
The ground will move by at most 0.1 nanometers per second, Fernando and colleagues calculated. “It’s incredibly small,” he says. “But the seismometer is also incredibly sensitive.”
The team may be able to catch that tiny signal because they know exactly when and where the impact will happen. If the lander does pick up the signal, it will tell scientists something about how fast seismic waves travel through the ground, a clue to the details of Mars’ interior structure. And even if they don’t feel anything, that will put limits on the waves’ speed. “It still teaches us something,” Fernando says.
The InSight team hopes to also feel vibrations from Tianwen-1 when its rover touches down in May. “Detecting one would be great,” Fernando says. “Detecting two would be like, amazing.” More

Amino acids in a meteorite — Science News, December 5, 1970
[Researchers] present evidence for the presence of amino acids of possible extraterrestrial origin in a meteorite that fell near Murchison, Victoria, Australia, Sept. 28, 1969.… If over the course of time their finding becomes accepted … it would demonstrate that amino acids, the basic building blocks of proteins, can be and have been formed outside the Earth.
Update
Scientists confirmed in 1971 that the Murchison meteorite contained amino acids, primarily glycine, and that those organic compounds likely came from outer space (SN: 3/20/71, p. 195). In the decades since, amino acids and other chemical precursors to life have been uncovered in other fallen space rocks. Recent discoveries include compounds called nucleobases and sugars that are key components of DNA and RNA. The amino acid glycine even has been spotted in outer space in the atmosphere of comet 67P/Churyumov-Gerasimenko. Such findings bolster the idea that life could exist elsewhere in the universe. More

For the first time in almost half a century, scientists are going to get their hands on new moon rocks.
The Chinese space agency’s Chang’e-5 spacecraft, which landed on the moon around 10:15 a.m. EST December 1, will scoop up lunar soil from a never-before-visited region and bring it back to Earth a few weeks later. Those samples could provide details about an era of lunar history not touched upon by previous moon missions.
“We’ve been talking since the Apollo era about going back and collecting more samples from a different region,” says planetary scientist Jessica Barnes of the University of Arizona in Tucson, who works with lunar samples from the American and Soviet Union missions of the 1960s and 1970s. “It’s finally happening.”
Chang’e-5, the latest in a series of missions named for the Chinese moon goddess (SN: 11/11/18), took off from the China National Space Administration’s launch site in the South China Sea on November 23 and landed in volcanic flatlands on the northwest region of the moon’s nearside.

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The lander, equipped with a scoop and a drill, will collect about two kilograms of soil and small rocks, possibly from as deep as two meters below the moon’s surface, says planetary scientist Long Xiao of China University of Geosciences in Wuhan.
The spacecraft has to work fast. With no internal heating mechanism, it has no defenses against the extremely cold lunar night, which can reach –170° Celsius. The entire mission has to fit within one lunar day, about 14 Earth days.
After the lander collects the sample, a small rocket will bring the lander and the sample back to the orbiter perhaps as early as December 3, although the Chinese space agency has not released the official schedule.
Once in orbit, the moon material will be packaged into a return capsule and sent back to Earth. The capsule is expected to land in the Inner Mongolia region by December 17.
The last time new lunar samples were sent back to Earth was 1976, with the end of the Soviet Union’s Luna program. Between those missions and NASA’s Apollo missions, scientists on Earth have about 380 kilograms of moon material to study (SN: 7/15/19). “Perhaps for a long time people thought, been there, done that, when it comes to the moon,” Barnes says.
Two kilograms of new stuff might not sound like much next to what’s already in hand. But Chang’e-5 is returning samples from an entirely unexplored region. The landing site is in the Mons Rümker region in the northwest region of the nearside of the moon. Like the Apollo and Luna landing sites, Rümker is flat. “The engineering consideration is first, to be safe,” Xiao says.

All the Apollo and Luna missions visited ancient volcanic plains, where the rocks are between 3 billion and 4 billion years old. Rümker’s volcanic rocks are much younger, around 1.3 billion to 1.4 billion years old. In the ‘60s, scientists didn’t think the moon was still volcanically active that late. More recent studies from lunar orbit and from telescopes have suggested a more complicated volcanic past.
“With these new samples, we potentially add another pinpoint in our geologic history of the moon,” says Barnes. “We’ll get an idea of, what was the volcanic history like on the moon a billion years ago? That’s something we don’t have access to in the returned samples we already have.”
The Rümker region is also rich in potassium, rare-Earth elements and phosphorous, often called KREEP elements. Those elements were some of the last to crystalize out of the magma ocean that covered the young moon and can help reveal details of how that process happened. It’s an “exotic flavor” of material, says Barnes. “It’s a really different area, geochemically, to the rest of the moon.”
One of the biggest challenges for the mission will be drilling that material. The drill can’t change direction once it’s deployed, so it has to attempt to drill through anything directly below it. If the drill hits a large rock, it could fail. So the Chang’e-5 team is hoping for fine, loose soil, Long says.
Once the sample is back on Earth, it will be stored and cataloged at a curation center in Beijing. Then it will be distributed for scientists to do research.
“You can’t breathe easy on these types of missions until the samples are back and are safe in the curation place where they’re going to be held,” Barnes says.
The Chinese space agency plans to share samples with international scientists. A 2011 congressional rule makes it difficult for U.S. scientists to collaborate directly with China, so it’s unclear who will get to work with the rocks. But the discoveries that the new samples will enable go beyond international borders.
“It doesn’t matter who’s doing it,” says Barnes. “The whole world should be behind this mission and this endeavor. It’s a piece of history.” More

In the film The Martian, astronaut Mark Watney (played by Matt Damon) survives being stranded on the Red Planet by farming potatoes in Martian dirt fertilized with feces.
Future Mars astronauts could grow crops in dirt to avoid solely relying on resupply missions, and to grow a greater amount and variety of food than with hydroponics alone (SN: 11/4/11). But new lab experiments suggest that growing food on the Red Planet will be a lot more complicated than simply planting crops with poop (SN: 9/22/15).
Researchers planted lettuce and the weed Arabidopsis thaliana in three kinds of fake Mars dirt. Two were made from materials mined in Hawaii or the Mojave Desert that look like dirt on Mars. To mimic the makeup of the Martian surface even more closely, the third was made from scratch using volcanic rock, clays, salts and other chemical ingredients that NASA’s Curiosity rover has seen on the Red Planet (SN: 1/31/19). While both lettuce and A. thaliana survived in the Marslike natural soils, neither could grow in the synthetic dirt, researchers report in the upcoming Jan. 15 Icarus.
“It’s not surprising at all that as you get [dirt] that’s more and more accurate, closer to Mars, that it gets harder and harder for plants to grow in it,” says planetary scientist Kevin Cannon of the Colorado School of Mines in Golden, Colo., who helped make the synthetic Mars dirt but wasn’t involved in the new study.

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Soil on Earth is full of microbes and other organic matter that helps plants grow, but Mars dirt is basically crushed rock. The new result “tells you that if you want to grow plants on Mars using soil, you’re going to have to put in a lot of work to transform that material into something that plants can grow in,” Cannon says.
Biochemist Andrew Palmer and colleagues at the Florida Institute of Technology in Melbourne planted lettuce and A. thaliana seeds in imitation Mars dirt under controlled lighting and temperature indoors, just as astronauts would on Mars. The plants were cultivated at 22° Celsius and about 70 percent humidity.
Seeds of both species germinated and grew in dirt mined from Hawaii or the Mojave Desert, as long as the plants were fertilized with a cocktail of nitrogen, potassium, calcium and other nutrients. No seeds of either species could germinate in the synthetic dirt, so “we would grow up plants under hydroponic-like conditions, and then we would transfer them” to the artificial dirt, Palmer says. But even when given fertilizer, those seedlings died within a week of transplanting.
In lab experiments, lettuce was able to grow in Marslike soil from the Mojave Desert (pictured) as long as the soil was fertilized with nitrogen, potassium, calcium and other nutrients.Nathan Hadland
Palmer’s team suspected that the problem with the synthetic Mars dirt was its high pH, which was about 9.5. The two natural soils had pH levels around 7. When the researchers treated the synthetic dirt with sulfuric acid to lower the pH to 7.2, transplanted seedlings survived an extra week but ultimately died.
The team also ran up against another problem: The original synthetic dirt recipe did not include calcium perchlorate, a toxic salt that recent observations suggest make up to about 2 percent of the Martian surface. When Palmer’s team added it at concentrations similar to those seen on Mars, neither lettuce nor A. thaliana grew at all in the dirt.
“The perchlorate is a major problem” for Martian farming, says Edward Guinan, an astrobiologist at Villanova University in Pennsylvania who was not involved in the work. But calcium perchlorate may not have to be a showstopper. “There are bacteria on Earth that enjoy perchlorates as a food,” Guinan says. As the microbes eat the salt, they give off oxygen. If these bacteria were taken from Earth to Mars to munch on perchlorates in Martian dirt, Guinan imagines that the organisms could not only get rid of a toxic component of the dirt, but perhaps also help produce breathable oxygen for astronauts.
What’s more, the exact treatment required to make Martian dirt farmable may vary, depending on where astronauts make their homestead. “It probably depends where you land, what the geology and chemistry of the soil is going to be,” Guinan says.
To explore how that variety might affect future agricultural practices, geochemist Laura Fackrell of the University of Georgia in Athens and colleagues mixed up five new types of faux Mars dirt. The recipes for these fake Martian materials, also reported in the Jan. 15 Icarus, are based on observations of Mars’ surface from the Curiosity, Spirit and Opportunity rovers, as well as NASA’s Mars Global Surveyor spacecraft and Mars Reconnaissance Orbiter.
Each new artificial Mars dirt represents a mix of materials that could be found or made on the Red Planet. One is designed to represent the average composition across Mars, similar to the synthetic material created by Cannon’s team. The other four varieties have slightly different makeups, such as dirt that is particularly rich in carbonates or sulfates. This collection “expands the palette of what we have available” as test-beds for agricultural experiments, Fackrell says.
She’s now using her stock to run preliminary plant growth experiments. So far, a legume called moth bean, which has similar nutritional content to a soybean but is more drought resistant, has grown the best. “But they’re not necessarily super healthy,” Fackrell says. Future experiments could explore what nutrient cocktails help plants survive in the various fake Martian terrains. But this much is clear, Fackrell says: “It’s not quite as easy as it looks in The Martian.” More

Mars’ water is being skimmed off the top. NASA’S MAVEN spacecraft found water lofted into Mars’ upper atmosphere, where its hydrogen and oxygen atoms are ripped apart, scientists report in the Nov. 13 Science.
“This completely changes how we thought hydrogen, in particular, was being lost to space,” says planetary chemist Shane Stone of the University of Arizona in Tucson.
Mars’ surface was shaped by flowing water, but today the planet is an arid desert (SN: 12/8/14). Previously, scientists thought that Mars’ water was lost in a “slow and steady trickle,” as sunlight split water in the lower atmosphere and hydrogen gradually diffused upward, Stone says.
But MAVEN, which has been orbiting Mars since 2014, scooped up water molecules in Mars’ ionosphere, at altitudes of about 150 kilometers. That was surprising — previously the highest water had been seen was about 80 kilometers (SN: 1/22/18).
That high-up water varied in concentration as the seasons changed on Mars, with the peak in the southern summer, when seasonal dust storms are most frequent (SN: 7/14/20). During a global dust storm in 2018, water levels jumped even higher, suggesting dust storms lift water in a “sudden splash,” Stone says.
The top of Mars’ atmosphere is full of charged molecules that are primed for rapid chemical reactions, especially with water. So water up there is split apart quickly, on average lasting only four hours, leaving hydrogen atoms to float away (SN: 11/27/15). That process is 10 times faster than previously known ways for Mars to lose water, Stone and his colleagues calculated.
This process could account for Mars losing the equivalent of a 44-centimeter-deep global ocean in the past billion years, plus another 17-centimeter-deep ocean during each global dust storm, the team found. That can’t explain all of Mars’ water loss, but it’s a start. More

Detecting phosphine in Venus’ atmosphere made headlines, but reanalyses and new searches call into question the original discovery of the molecule. More

Comet 67P/Churyumov-Gerasimenko has its own version of the northern lights.
Observations taken by the Rosetta spacecraft reveal the comet’s aurora, which — unlike Earth’s eye-catching light shows — shimmers in invisible ultraviolet light, researchers report online September 21 in Nature Astronomy. Comet 67P joins comet C/Hyakutake 1996 B2, Mars (SN: 3/19/15), Saturn (SN: 4/6/20) and moons of Jupiter as known hosts of extraterrestrial auroras.
Electrons in the solar wind — a stream of charged particles continually flowing from the sun — interact with the gas surrounding 67P to create the auroral glow, planetary scientist Marina Galand of Imperial College London and colleagues report. Solar wind electrons are drawn toward the comet by an electric field surrounding 67P, similar to the way electrons cascade into Earth’s atmosphere to produce the northern and southern lights (SN: 7/25/14).
Electrons strike oxygen in Earth’s atmosphere to paint the sky red and green. But solar wind electrons strike water molecules in 67P’s coma, or shroud of gas. That shatters the water molecules and makes some of the resulting oxygen and hydrogen atoms glow ultraviolet. A similar water-smashing interaction creates auroras on Jupiter’s moons Europa and Ganymede (SN: 3/12/15).
Also unlike Earth, 67P has no magnetic field to steer incoming electrons toward the poles and form auroras with distinct patterns in the sky (SN: 2/7/20). If 67P’s ultraviolet aurora were visible, it would look like a diffuse halo around the comet.
Such cometary auroras could someday be used to probe variations in the solar wind, Galand says. That may lead to better forecasts for space weather, which can mess with satellites and power grids (SN: 7/5/18). More

Earth’s deep stores of water may have been locally sourced rather than trucked in from far-flung regions of the solar system.
A new analysis of meteorites from the inner solar system — home to the four rocky planets — suggests that Earth’s building blocks delivered enough water to account for all the H2O buried within the planet. What’s more, the water produced by the local primordial building material likely shares a close chemical kinship with Earth’s deep-water reserves, thus strengthening the connection, researchers report in the Aug. 28 Science.
Earth is thought to have been born in an interplanetary desert, too close to the sun for water ice to survive. Many researchers suspect that ocean water got delivered toward the end of Earth’s formation by ice-laden asteroids that wandered in from cooler, more distant regions of the solar system (SN: 5/6/15). But the ocean isn’t the planet’s largest water reservoir. Researchers estimate that Earth’s interior holds several times as much water as is found at the surface.
To test whether or not the material that formed Earth could have delivered this deep water, cosmochemist Laurette Piani of the University of Lorraine in Vandœuvre-lès-Nancy, France, and colleagues analyzed meteorites known as enstatite chondrites. Thanks to many chemical similarities with Earth rocks, these relatively rare meteorites are widely thought to be good analogs of the dust and space rocks from the inner solar system that formed Earth’s building blocks, Piani says.

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She and her team measured the abundance of hydrogen in these meteorites — a proxy for how much H2O they could produce — and calculated that local interplanetary debris had the potential to deliver at least three times as much water as is found in all the oceans. The meteorites don’t contain water, Piani says. Rather, they house enough of the raw ingredients to create water when heated.
In the meteorites, the team also found a close match to the type of water found in Earth’s mantle. A smattering of all water molecules on Earth contain a heavy variant of hydrogen known as deuterium. The ratio of deuterium to hydrogen in the enstatite chondrites lies within the range measured in Earth’s deep water. That similarity, the team argues, makes a strong case for local building blocks being the source of much of the planet’s water.
“This work is something I wanted to do myself or had been waiting for someone to do,” says Lydia Hallis, a planetary scientist at the University of Glasgow in Scotland. In 2015, she led a team that measured the deuterium abundance in lava plumes that tap deep into Earth’s mantle (SN: 11/12/15). “I’m really happy that [the new data] sits within the region where our previous data from deep mantle samples is sitting.”
Hallis and others stress that these new measurements are difficult. Once the meteorites hit the ground, they quickly absorb hydrogen from Earth’s environment. “They did a really good job of picking the right meteorites and making the right measurements,” she says. “This is pretty convincing that this hydrogen that’s measured is from the enstatite chondrites rather than from terrestrial contamination.”
The enstatite chondrites could have also contributed a lot of water to the oceans as well — but they are not the full story. The deuterium-hydrogen ratio in ocean water, which is a bit higher than that of mantle water, is better matched to the ratio found in icy asteroids from the outer solar system. “We still need a bit of water coming from the outer solar system,” Piani says. So, while local materials may have delivered the bulk of Earth’s water, the oceans were likely topped off a bit later by collisions with remote space rocks. More